Joe’s Weather Blog: OK Now But Arctic Cold Lurks

Joe’s Weather Blog: OK Now But Arctic Cold Lurks

Lots of clouds across the region overnight and this AM have kept temperatures from free-falling. This AM our low was 45° which is about 5° below average for this time of the year…Clouds today will keep temperatures in check but eventually we should see some breaks and sunshine allowing highs to end up close to 60° or so…also about 5° below average…it’s gets better tomorrow with highs well into the 60s and sunshine.

There is a weak system that will skirt past the area on Friday…I can’t rule out some showers/sprinkles with this which is if happens looks to occur during the AM into early PM hours…that could be a sneaky chilly day with light rain falling into low dewpoint air (dry air) dropping temperatures as the minor event unfolds…weekend looks great by the way. We’ve certainly had a stretch of great fall weekends in these parts, and this one should follow suit!

For gardener’s thus far we’ve dodged a lot of the frost bullets that have been fired at us…but that may come to an end next week…and we may also see our first freeze and it very well may be a hard freeze. We continue to be on a roller-coaster ride with some ups and downs, although so far they’ve been mostly minor. Next week though, especially from Tuesday on may be a different story as much colder air will come in 2 stages with one chunk followed by another more potent shot of cold air…which should send temperatures tumbling. So what is going to trigger this change?

When we get big deliveries of cold air from the Arctic region there is typically a series of events that has to happen…1) would be a BIG dip in the jetstream in the eastern part of the country and the other would be a big rise northward of the jetstream in the western US…but the key is that it has to poke way to the north through W Canada. This series of events floods the western parts of Canada and AK with warm air, and dislodges the colder air and releases it into the central and eastern part of the US. Here is a look at the EURO model showing the sequence of events starting…this map if for MON @ 7PM.

Colder air should be on our door step around this time and getting ready to move in on Tuesday…this will be a significant cold shot. The key to the next cold shot is a disturbance that will move into W Canada early next week and ride into and over the big “ridge” out west. That disturbance will then come down into the US and potentially deliver the another shot of the cold towards the end of the week.

Here is the same map above except let’s jump ahead to NEXT FRI at 7PM…and things are evolving. The ridge out west is MUCH sharper and poking all the way up towards the Arctic Circle…the key to the delivery of the 2nd shot of cold is moving into S Canada.

So the maps above represent the flow at 500 mbs or about 18,000 feet. Now let’s move down in the atmosphere to about 5000 feet where we can get a better handle of the airmasses and this next map is more telling of the coming cold. It shows the anomalies at that level (how much above/below average)

Click on this map (like all the others to make it larger). The maps are in 24 hr increments starting in the upper left @ 7PM MON-7PM TUE-7PM WED then 7PM THU and finally in the lower right 7PM FRI. Notice all the blue/purples around in the Plains states…that’s cold air! Almost 15° C/27°F below average at that level and should this be close to valid will have us looking into the record books for potential record lows (mid 20s) for the middle/end of next week.

One thing working in our favor with these early season Arctic outbreaks is a lack of snowcover at this point in time

So the cold air will be moving over bare ground…that combined with the decent late October sunshine should help to modify the airmass a bit as it moves towards the Plains…still though that is some cold air which potentially can keep daytime highs in the 40s!

Here is the way the EURO plays things out from a temperature standpoint over the next 10 days.

The GFS ensembles are aboard as well…here is a look at the 5000 ft temperatures over the next 16 days, the rest of the month…you can get an idea of the anomalies at that level and see the colder air move in and then move by around Halloween.

Get those outdoor chores down while the weather is reasonable for the next week or so because the clock is ticking and the cold air may be unleashed soon for about 5-7 days!